In U.S. Pat. No. 2,957,803, granted Oct. 25, 1960 and titled "Method of Preparing Suspension of Insecticides", is disclosed a method of forming a stable suspension of water insoluble organic pesticides comprising the steps of forming a liquid emulsion of fat or oil in water made heavier by a substance soluble in the water, introducing the solids into the liquid emulsion, to particles of a fineness of the order of 5 to 15 microns while agitating the liquid and solids together.
In U.S. Pat. No. 3,184,380, granted May 18, 1965 and titled "Stabilization of Concentrated Suspensions of Pesticide Particles", is disclosed a method of improving the uniformity of such a suspension when the chemicals being suspended have certain characteristics. It applies to certain water insoluble pesticide chemicals having a crystalline form in the range of temperatures at which they are stored and used. They also (1) must have a melting point below its decomposition temperature and below the boiling point of the suspending solution, or (2) be substantially totally soluble in the coating fat below the boiling point of the suspending liquid and below its decomposition temperature. A suspension made according to U.S. Pat. No. 2,957,803 can then be heated until melting occurs. After cooling the resulting suspension has a much finer and/or uniform particle size.
We have discovered that we are now able to improve the uniformity of the suspension for an additional pesticide. The present method is directed to the synthesis of Ziram, which has utility as a pesticide when applied to growing crops by spraying in a suspension.
U.S. Pat. No. 2,492,314 discloses a direct reaction method for synthesizing insoluble metal salts of substituted dithiocarbamic acids, including Ziram. The chemical system used for synthesis is essentially dry, although some of the listed examples discuss the use of water for mixing purposes only. The resulting products are stated to be dry.